1. Field of the Invention
The present invention relates to a three-dimensional vision endoscope apparatus for three-dimensionally displaying a subject for observation.
2. Description of the Related Art
In recent years, endoscopes permitting observation of organs in body cavities and enabling a variety of treatment procedures have been put to use. Endoscopes for industrial use have been utilized to observe and inspect boilers, gas-turbine engines, pipes in a chemical plant, and insides of engines of automobiles in order to see if flaws and corrosion are present.
The endoscope for observing organs in body cavities falls into a class of a flexible endoscope whose insertional part is flexible and insertable into a body cavity through the oral cavity for observation and evaluation of a lesion, and a rigid endoscope whose insertional part is rigid and insertable straight into an intended region for observation and evaluation of a lesion.
The flexible endoscope, which is of an optical type, employs flexible image guide fibers as an image transmitting means. The rigid endoscope offers excellent sniping efficiency because of the rigid insertional part thereof, wherein a relay optical system is usually employed as an image transmitting means.
The endoscope including the rigid endoscope is divided into a type that permits observation of an optical image with naked eyes and a type that uses a solid-state imaging device such as a charge coupled device (CCD) as an imaging means. Whichever type of endoscope is employed, the inside of a body cavity that is an object of examination is visualized as, for example, a plane without depth perception. It is, therefore, difficult to observe the fine irregularities on the surface of an inner wall of a body cavity that provide a very important diagnostic guideline.
Japanese Patent Laid-Open No. 57-69839 has proposed, for example, a three-dimensional vision endoscope in which ends of a pair of image guides are provided with objective lenses and the other ends thereof are provided with eyepieces. In the three-dimensional vision endoscope, the pair of image guides are lying through an insertional part of the endoscope and a convergence angle formed between an objective lens and an object point of observation is set to an angle permitting three-dimensional vision. Thus, stereoscopic observation is enabled.
The foregoing three-dimensional vision endoscope is based on a flexible endoscope. In a three-dimensional vision endoscope based on a rigid endoscope (hereinafter, referred to as a three-dimensional vision rigid endoscope), two relay optical systems are placed in parallel with each other. Optical images provided by the two relay optical systems are processed by CCDs or the like, thus enabling three-dimensional observation. For example, U.S. Pat. No. 4,924,835 describes an arrangement that comprises two light transmitting means and two shutters, and that enables three-dimensional observation by shielding two observation images, which are provided by the light transmitting means, alternately using the shutters. The three-dimensional vision endoscope provides an observer with left and right optical images having a parallax between them. The observer looks into eyepieces through special glasses, and thus views a three-dimensional image. Alternatively, left and right images of a subject are displayed on a monitor to provide a three-dimensional image. The above three-dimensional vision endoscope is included in a three-dimensional vision rigid endoscope apparatus. The three-dimensional vision rigid endoscope apparatus converts an observation image into an electrical signal using an imaging means, processes the electrical signal, and then displays left and right images on a monitor screen concurrently or alternately.
In either of the techniques; that is, whether left and right images are displayed on a monitor concurrently or alternately, left and right images of a subject displayed on the monitor become consistent when viewed through the aforesaid glasses. Eventually, a stereoscopic image is observed.
However, in some three-dimensional vision rigid endoscopes each having two optical systems, the optical systems are formed independently of imaging means and made freely dismountable. In this kind of three-dimensional vision rigid endoscope, when optical systems, which are different from each other in orientation of a visual field, angle of view, and picture size, are used in combination with imaging means, the optical axes of the optical systems may become misaligned to mismatch left and right images in an observation screen on a monitor. A difference in the magnification or depth of field between the optical systems may lead to a mismatch in display position between left and right images, which disables the capabilities for three-dimensional recognition of a visualized subject. The mismatch in display position between left and right images sometimes occurs due to a mechanical impact not only in a three-dimensional vision rigid endoscope in which optical systems are dismountable but in a three-dimensional vision endoscope in which optical systems are united with imaging means.
The left and right images have a parallax between them. Even when the contours of the left and right images are mismatched, if a quantity of mismatch in display position between the left and right images is within an approximate range, an observer can see a consistent image while having no sense of unnaturalness but a sense of three-dimensionality.
However, when a quantity of mismatch in display position between left and right images is too large, the left and right images do not become consistent with each other. The observed image is therefore not recognized three-dimensionally, which causes an observer to feel terrible fatigue. Thus, the three-dimensional visualization procedure has been found a nuisance.